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AQA BIOL2 Biology Unit 2 Exam - 26th May 2011 watch

  • View Poll Results: Are you resitting this unit?
    YES!
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    NO!
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    What time is the exam tomorrow?
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    Depends on your centre. I believe they have to take place between 1-2pm. So if you're not sure, get there before 1.
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    (Original post by Benevolence)
    What time is the exam tomorrow?
    In the afternoon. Depends when your college starts it. I have it at around 1:15,
    urgh......... cant bear the thought of sitting in there till 3pm :O
    Good luck!!!!!!
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    Im more scared of maths at 9:30 lols
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    (Original post by Rahul.S)
    going over biol2...probz finish all papers by late 2night
    Yo chem 1 mark scheme geeeeezer wa u think coming up??
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    good luck to evy1!!
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    (Original post by lolo-x)
    Insects have an waterproof exoskeleton made of chitin which prevents unwanted water loss.
    They have tracheae which lead to holes in the surface of their exoskeleton called spiracles that can close to prevent evaporation of water when the insect is inactive. Branching off from the tracheae are tracheoles: the site of gas exchange in insects.

    Smaller insects and inactive ones just use diffusion for gas exchange.

    Larger insects during intense activity (e.g. flight) require more ATP so cells need more oxygen (because muscle contraction increases, so need for ATP increases, so rate of resp increases, so more oxygen is required to maintain rate of resp). Larger insects increase their oxygen supply by pumping their abdomen so more air moves in and out of the trachea

    Water is withdrawn from the ends of the tracheoles during exercise because oxygen diffuses faster in air than in water, and to decrease the pressure so that air is pulled in faster.
    when insects respire an aerobically, they produce lactic acid in muscle cells which lowers the water potential :. so water diffuses from tracheoles into muscle cells by osmosis.this makes diffusion of O2 faster, so actively respiring cells get O2 quicker.

    do we need to knw this stuff coz i didnt find in the syllabus.
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    In general what do we need to know about the variation topic..Tx alot
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    good luck everyone!!
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    How do you work out questions 2b in the jun10 paper, the diameter question.
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    (Original post by al_habib)
    when insects respire an aerobically, they produce lactic acid in muscle cells which lowers the water potential :. so water diffuses from tracheoles into muscle cells by osmosis.this makes diffusion of O2 faster, so actively respiring cells get O2 quicker.

    do we need to knw this stuff coz i didnt find in the syllabus.
    No we don't.
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    (Original post by Some random guy)
    No we don't.
    Do we need to talk about water potential at all for the insects gas exchange?
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    We need to know how they limit water loss. Water potential questions will be to do with plants.
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    (Original post by Some random guy)
    We need to know how they limit water loss. Water potential questions will be to do with plants.
    Ok so just like sayin water proof coverings/spiracle are opened and closed by valves etc?
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    (Original post by ImaBarbieGirl)
    but the gamete in that question does have 6 chromosomes
    That's the cell, the question below you have to draw a gamete from that cell so it will have half the number of chromosomes = 3
    Then the question about the number of combinations asks about the gamete not the original cell
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    (Original post by Master.K)
    How do you work out questions 2b in the jun10 paper, the diameter question.
    Magnification = Image / Object
    so..
    Object = Image / Magnification

    You then just put the numbers into the equation and there's the answer
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    (Original post by Master.K)
    How do you work out questions 2b in the jun10 paper, the diameter question.
    Measure the diameter of the lumen in the picture and divide it by 8, the magnification.
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    (Original post by Master.K)
    Ok so just like sayin water proof coverings/spiracle are opened and closed by valves etc?
    spricles are insectes not plants. But yes talk about waxy waterproff cuticles. talk about curtain xerophytic adaptations such as stoamata in pits which traps moist humid air, this reduces the concentration gradient of water. hairs trap moist humid air and also reduce the concentration gradient of water. Also talk about maybe how guard cells are turgid (open stomata) when hydrated and how they are flaccid (close stomata) when dehydrated and relate this, the fact the stoma are closed reduces h20 loss.
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    Am I right in thinking we don't need to know how to work out standard deviation?
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    (Original post by emillie)
    Am I right in thinking we don't need to know how to work out standard deviation?
    no idea, my teacher mantioned it but sheis stupid so dunno. I doubt we would but im scared
 
 
 
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